Replace .claude directory with git submodule

[MaxGhenis]

Summary

This PR replaces the local .claude directory with a proper git submodule, enabling consistent multi-agent development workflow across PolicyEngine repositories.

Changes

• 🔄 Replace local .claude agent files with git submodule pointing to https://github.com/PolicyEngine/.claude.git
• ➕ Add comprehensive Python .gitignore file
• ➕ Add .gitmodules configuration

Benefits

• ✅ Consistent multi-agent workflow across all PolicyEngine repos
• ✅ Centralized updates to agent configurations
• ✅ Follows the pattern established in policyengine-us

File Changes

• Deleted: 8 local .claude/agents/*.md files (2,016 lines removed)
• Added: .claude submodule, .gitmodules, .gitignore (162 lines added)
• Net reduction: ~1,854 lines

🤖 Generated with Claude Code